Various methods of chemical vapor deposition have been proposed for forming high purity optical fiber glasses having extremely low cation impurities and OH ions present in the glass structure. One method proposed for the manufacture of high purity optical fiber glass is that described within U.S. patent application Ser. No. 804,209 filed June 7, 1977 and entitled METHOD OF FABRICATING LOW LOSS OPTICAL FIBER USING A GRAPHITE TUBING.
This method uses a highly purified carbon deposition substrate for chemically distilling high purity materials on the inner surface thereof. The carbon is in the form of a cylinder and provides an environmental enclosure for the material as it is deposited. After a quantity of highly purified material is deposited on the inner surface of the carbon cylinder, the carbon is removed generally by grinding. The material can also be separated by deposition upon a split mold and removing the material from the mold.